This U19 TRIAD Technology Development proposal describes an innovative program aimed at developing a high-performance, pro-inflammatory and non-tolerogenic vaccine delivery system based on the dendritic cell targeting anti-DEC-205 antibody. The success of anti-DEC-205 as a stimulator of strong inflammatory immune responses depends on co-administration of non-specific dendritic cell maturation factors. In their absence, anti- DEC-205 induces antigen-specific tolerance rather than immunity. Because of the dangers associated with nonspecific activation of the immune system, we propose to develop a modified pro-inflammatory and nontolerogenic anti-DEC-205 antibody. We have discovered a set of natural regulatory T-cell epitopes derived from human immunoglobulins that induce tolerance by stimulating regulatory T cells. We have verified experimentally that these epitopes generate antigen-specific expansion of regulatory T cells and suppress inflammatory immune responses. We hypothesize that regulatory T-cell epitopes contained in anti-DEC-205 promote a tolerogenic reaction that is only overcome through co-administration of non-specific immunostimulators. We expect that modification of these epitopes will significantly diminish tolerogenicity, enabling use of anti-DEC-205 as a stand-alone, high performance antigen delivery system. We will de-tolerize anti-DEC-205 by epitope modification in a two-stage process beginning first in a (humanized) mouse model system and progressing to human blood samples. Using TRIAD Toolkit Core immuno-informatics algorithms, we will reengineer anti-DEC-205 such that key amino acids in its regulatory T-cell epitopes are replaced with those that are experimentally shown to interfere with HLA binding. We will then (1) produce a set of antibody variants recombinantly conjugated to test antigens including vaccine candidates identified in TRIAD Research Projects, (2) identify de-tolerizing mutations that do not interfere with dendritic cell targeting, and (3) evaluate variants for reduced tolerogenicity, as well as for enhanced immunogenicity for vaccine antigens.